First, Search the Library Catalog for books on ironclads and on the US Navy during the Civil War.
Then, for articles, go back to the Library home page and click on the Research by Subject tab. Select Humanities.
Biographical sketches of John Ericsson may be found in CREDO Reference ; Oxford Reference; and the Biographies in Context databases.
Articles on Ericsson and the ironclad "Monitor", may also be found in the Academic Search Premier and Jstor databases (search Ericsson and ironclads).
See also Google Patents for Ericsson's patented inventions ("John Ericsson" AND "New York"), paying special attention to the dates of filing. You may also wish to see the patent filed by Theodore Timby for a revolving gun turret that was used by Ericsson on the Monitor.